Firefighters are gaining ground in their efforts to suppress large wildfires burning in the south-east states of the US, but several blazes continue to creep into new areas covering a total of more than 120,000 acres.

There are 44 uncontained large fires in the South, covering a total of more than 120,000 acres, national fire officials said Tuesday. In Watauga County, North Carolina, a fire that began Monday evening spread Tuesday to cover about 400 acres and threaten 55 homes in an area east of Blowing Rock, the Watauga County Fire Marshal's Office said; AP reported.

He said officials do not know how the fire started. Arson investigations are underway in Georgia, Tennessee, North Carolina and Kentucky. In Tennessee, firefighters have responded to 27 new fires since Friday, and 19 of them are suspected arsons, the Tennessee Department of Agriculture reported.

Most of those recent blazes are relatively small, the largest being a 452-acre wildfire north-west of Knoxville. The southern forests have caught fire amid a relentless drought.

More than 47 million people are now living in drought areas, which stretch from Oklahoma and Texas all the way east to the Carolinas and parts of Virginia, according to the latest information from the National Drought Mitigation Centre. In recent days, high winds and falling leaves have been among the toughest challenges firefighters have faced, authorities say.